The term “biological deposits” used herein refers generally to deposits of material of biological origin, e.g. plaque, bacteria, tartar, calculus etc. which are generally regarded as undesirable for dental hygiene. Dental plaque is a complex organic deposit generated in part by the activity of bacteria upon the teeth or upon contamination, e.g. food deposits on the teeth, and is an undesirable precursor to tooth decay and the development of dental caries.
It is desirable to detect such deposits on the teeth before removing them, for example by toothbrushing, as detection indicates the areas at which dental cleaning effort should be concentrated. Such deposits can be difficult to detect in situ in vivo on the teeth. It is especially important to detect dental plaque. For detection of plaque it is known to use fluorescence measurement, in which incident radiation is directed at the surfaces of teeth, and fluorescence radiation having characteristics associated with the presence of biological deposits is emitted from the teeth and is detected.
In the state of the art there are two general methods for detecting dental plaque, using respectively primary fluorescence in which the fluorescence of dental plaque or other dental material itself is monitored, and secondary fluorescence in which teeth suspected of bearing plaque are treated with a fluorescent label material which preferentially binds to dental plaque, and the fluorescence emission of the label material at areas of the tooth at which it has bound is detected to indicate the presence of dental plaque. Patent publications WO 92/06671, U.S. Pat. No. 5,382,163, DE 29704185, DE 29705934, EP 0774235, and also WO 97/01298 (Phillips) disclose methods of this type and devices for performing these methods. GB 9810471.4 filed on 16 May 1998 and internationally filed as PCT/EP99/03273, the contents of which are included herein by way of reference, discloses a further method and apparatus for detecting biological deposits on tooth surfaces using fluorescence. One form of the apparatus disclosed in PCT/EP99/03273 comprises a toothbrush head having a bundle of optical fibres extending through it to direct incident radiation at a test tooth surface, and to collect emitted radiation from the test tooth surface.
It is usually a requirement of such methods that incident radiation is directed at the surface of the teeth under examination and that consequent fluorescence emission radiation from the surface of the teeth is collected. WO 98/1071 1 discloses a toothbrush provided with a head which is made of a monolithic body of an optically transparent materials for the purpose of directing light towards the surfaces of the teeth. In WO 98/10711 this radiation is for the purposes of therapy not for detection of biological deposits.
Those of the above-mentioned devices which are toothbrushes generally use bundles of optic fibres passing through the head and body of the toothbrush to both direct incident radiation to the head and collect emitted radiation from the head. It is an object of this invention to provide a toothbrush of the above-described type having an improved means for directing incident radiation onto the surface of teeth and for collecting radiation emitted from the surface of teeth in response to the incident radiation.